Vertical Support Research Articles

Adaptive finite element analysis of steel girder deck pavement

This paper shows a more exact and practical finite element model of the steel girder deck pavement. Based on Mindlin thick plate theory, a 12-node solid thick plate element was constituted to analyze the pavement. The computation result was compared with that by traditional 4-node and 8-node thick plate finite element, and is satisfactory. A combined plate beam element method is presented to investigate the stiffened plate. A 6-node solid thin plate element was constituted to analyze the top plate based on Kirchhoff thin plate theory. The stiffeners acting as the vertical supporting function mainly are taken as Euler beam elements. A method of using the linear interpolation to realize the longitudinal displacement and the cubic Hermite interpolation to the vertical displacement is presented to analyze the stiffeners. In addition, it is essential to consider the displacement coordination between the top plate and stiffeners. A node-to-node contact scheme, which is applicable for three-dimensional contact analyses involving large deformations, was used to treat the contact problem between pavement and stiffened plate by Lagrange multiplier methods.

Nonlinear vibration isolation of a viscoelastic beam

In this paper, the transmissibility of a viscoelastic beam supported by vertical springs is defined by proposing a new vertical elastic support boundary. By contrasting with the viscoelastic beam with rigid vertical supports and the rigid rod with vertical elastic support ends, the necessity of the transmissibility of an elastic structure with vertical elastic supports is proved. In order to approximately solve the steady-state responses of the nonlinear transverse vibration of the viscoelastic beam under periodic excitation, the harmonic balance method in conjunction with the pseudo arc-length method is adopted. The numerical results are calculated to confirm the approximate analytic results. The comparison between the rigid rod and the elastic beam shows that neglecting the bending vibration of the structures will underestimate the frequency range in which the elastic support produces an effective vibration isolation. On the other hand, the comparison between the rigid support and the spring support demonstrates that ignoring the elasticity of the support ends will create a false understanding of the force transmission of elastic structures. In general, this paper presents the necessity of studying the force transmission of elastic structures with elastic supports. Moreover, this paper will become the beginning of the study of the vibration isolation of the elastic structure.

Transmissibility of Bending Vibration of an Elastic Beam

This paper proposes an isolation transmissibility for the bending vibration of elastic beams. At both ends, the elastic beam is considered with vertical spring support and free to rotate. The geometric nonlinearity is considered. In order to implement the Galerkin method, the natural modes and frequencies of the bending vibration of the beam are analyzed. In addition, for the first time, the elastic continuum supported by boundary springs is solved by direct numerical method, such as the finite difference method (FDM). Moreover, the detailed procedure of FDM processing boundary conditions and initial conditions is presented. Two numerical approaches are compared to illustrate the correctness of the results. By demonstrating the significant impact, the necessity of elastic support at the boundaries to the vibration isolation of elastic continua is explained. Compared with the vibration transmission with one-term Galerkin truncation, it is proved that it is necessary to consider the high-order bending vibration modes when studying the force transmission of the elastic continua. Furthermore, the numerical examples illustrate that the influences of the system parameters on the bending vibration isolation. This study opens up the research on the vibration isolation of elastic continua, which is of profound significance to the analysis and design of vibration isolation for a wide range of practical engineering applications.

The Role of Friction in the Static Equilibrium of a Fixed Ladder: Theoretical Analysis and Experimental Test

In a recent publication the author derived and experimentally tested several theoretical models, distinguished by different boundary conditions at the contacts with horizontal and vertical supports, that predicted the forces of reaction on a fixed (i.e. inextensible) ladder. This problem is statically indeterminate since there are 4 forces of reaction and only 3 equations of static equilibrium. The model that predicted the empirical reactions correctly used a law of static friction to complement the equations of static equilibrium. The present paper examines in greater theoretical and experimental detail the role of friction in accounting for the forces of reaction on a fixed ladder. The reported measurements confirm that forces parallel and normal to the support at the top of the ladder are linearly proportional with a constant coefficient of friction irrespective of the magnitude or location of the load, as assumed in the theoretical model. However, measurements of forces parallel and normal to the support at the base of the ladder are linearly proportional with coefficients that depend sensitively on the location (although not the magnitude) of the load. This paper accounts quantitatively for the different effects of friction at the top and base of the ladder under conditions of usual use whereby friction at the vertical support alone is insufficient to keep the ladder from sliding. A theoretical model is also proposed for the unusual circumstance in which friction at the vertical support can keep the ladder from sliding.

Reactive balance to unanticipated trip-like perturbations: a treadmill-based study examining effect of aging and stroke on fall risk

ABSTRACT The purpose of this study was to examine the mechanism of fall risk in community-dwelling ambulatory hemiplegic stroke survivors when exposed to a sudden, trip-like support surface perturbation in standing. Participants (n = 14 / group) included stroke survivors, Age-similar older controls (AC), and Young controls (YC) experienced trip-like perturbation on a motorized treadmill. The primary outcomes were COM state control (measured as COM position (XCOM/BOS) and velocity (VCOM/BOS) relative to the base of support (BOS)) and the vertical limb support recorded as the extent of hip descent. All participants demonstrated forward loss of balance (FLOB) followed by an equal first compensatory step length. At step touchdown, stroke survivors demonstrated lower COM state stability and increased trunk flexion than the YC group. Stroke survivors also demonstrated greater hip descent than YC and AC groups, as they first stepped with their non-paretic limb. For the second compensatory step, the stroke survivors stepped with their paretic limb. However, unlike the AC group, they were unable to control VCOM/BOS despite a longer compensatory step. In conclusion, poor control of COM state, impaired trunk control and inability of the paretic limb to provide vertical limb support may explain the higher fall-risk in stroke survivors.

Vertical Shaft Support Improvement Studies by Strata Grouting at Aquifer Zone

The shaft lining failure which occurs in deep alluvium is a sudden coal mine hazard. The strata grouting is one of the treatment methods for the shaft lining failure. To investigate the impact of grout injection pressure on the shaft lining, the field measurement and the numerical analysis of the shaft lining stress variation during the grouting were conducted. To improve the strata grouting, the underground continuous impervious curtain (UCIC) is proposed as a new method by using the chain conveyor cutter technique without the impact on the shaft lining. The effects of the new method were also analyzed by means of the numerical methods. The results show that the strata grouting in the deep alluvium needs a high injection pressure, and in the horizontal direction, the shaft lining sustains the repeat tensile and compressive force during the grouting process. The negative influence of strata grouting on the stability of the shaft lining is obvious and serious. The UCIC built around the shaft lining can restrain the stress concentration induced by the aquifer drawdown. The triangular UCIC has a similar effect as that of the vertical one, and the small angle is better for preventing the shaft lining failure.

Analysis of transverse vibration and stability issues of discrete-continuous elastic systems with nonlinearly variable parameters

The work is devoted to methods of analysis of vibrations and stability of discrete-continuous, multi-parameter models of beams, shafts, rotors, vanes, converting to homogeneous and one-dimensional. The properties of Cauchy's influence function and the characteristic series method were used to solve the boundary problem. It has been shown that the methods are an effective tool for solving boundary problems described by ordinary fourth-and second-order differential equations with variable parameters. Particular attention should be paid to the solution of the border problem of two-parameter elastic systems with variable distribution of parameters. Universal beam-specific equations with typical support conditions including vertical support, which do not depend on beam shape and axial load type, are recorded. The shape and type of load are considered in the form of an impact function that corresponds to any change in cross-section of the support and continuous axial load, so that the functions describing the stiffness, the mass and the continuous load are complete. As a result of the solution of the boundary vibration problem of freely bent support and any change in its cross-section, loaded with any longitudinal load, arranged on the resilient substrate, strict relations between the own frequency parameters and the load parameters were derived. Using the methods, simple calculations were made, easy to use in engineering practice and conditions of use were given. Experimental studies have confirmed the high accuracy of theoretical calculations using the proposed methods and formulas.

Damage Assessment of an RC Pier under Noncontact Blast Loading Based on P‐I Curves

Since the 9.11 attacks in New York, terrorist attacks, military strikes, and accidental explosions have caused serious damage to various infrastructures around the world. Accidental traffic explosions in bridge engineering have occurred frequently due to the increasing firework truck on the bridge and heavy fuel oil ships under the bridge. Besides, intentional car bomb explosions in terrorist attacks and military assaults are significant threats to the bridge structure. Bridge pier is a particularly important component of the overall bridge structure due to its vertical support capacity. Therefore, the damage of reinforced concrete (RC) piers under blast loading should be studied. In this paper, the pier is simplified as a single degree of freedom (SDOF) system based on energy equality, and the blast loading distribution on the surface of the pier is simplified as a uniform distribution. Then, the P‐I curves of an RC pier are obtained based on the SDOF system and a uniform distribution blast loading to quickly evaluate the damage extent of an RC pier so that the P‐I curves and fitting formulas for different damage extents can be used for practical engineering. After a numerical simulation verification, the P‐I curves and fitting formulas based on the simplified method can supply a rapid and effective method for engineers to assess the postexplosive damage of an RC pier.

Interaction of collar roof with the bottom support structure of a building

Collar roofs belong to the traditional structures used for roofing buildings. In present, the collar roofs are widely used for their ability to omit internal vertical support structures (columns, support walls), which might be sometimes a complication during a design of the layout of the building. Collar roof acts on the bottom support structure of the building by quite big lateral horizontal forces. These forces are being often neglected in common practice. This fact leads to failures of the bottom support structures. Reinforced concrete rim made on the top of the brick wall is one of the methods, how to deal with these horizontal forces. The article deals with the interaction. The article deals with the interaction between the structure of the collar roof and the reinforced concrete rim.

Experimental analysis of railway track settlement in transition zones.

Transition zones in railway tracks are the locations with considerable changes in the vertical support structures. Due to the differential stiffness and settlement in the open track and the engineering structure resulting in the dynamic amplification of the wheel forces, track settlement is usually observed in the approaching zones. The settlement in transition zones is detrimental to the track components and passenger comfort. This paper presents the results of the experimental analysis performed in three transition zones which were in various conditions. The dynamic displacements of rails due to passing trains were measured at multiple points (dynamic profile) in the approaching zones. The device employed is a contactless mobile device for measuring displacements, which is based on the digital image correlation technique. Because the operational parameters of the digital image correlation-based devices are important for measurement accuracy, prior to the in situ measurements, this device was tested in a laboratory to study the influence of the operational parameters, including the elevation/heading angles, the focal length of the cameras, and the measuring distance. After determining the optimal operational parameters for the railway field, multiple-point measurements were performed in the transition zones. The length of the approaching zone was studied first. Also, the dynamic profiles of the embankment–bridge and bridge–embankment transitions were analysed. Finally, by comparing the multiple-point displacements in the approaching zones in different conditions, it was found that the dynamic profile of the rail displacements has a good correlation with the track condition in the transition zone. The results are presented and discussed.

Modelling of the long-term behaviour of transition zones: Prediction of track settlement

Transition zones in railway tracks are the locations with considerable changes in the vertical support structures. Typically, they are located near engineering structures, such as bridges, culverts, tunnels and level crossings. In such locations, the variation of the vertical stiffness and the differential settlement of the track (when the foundation settles unevenly) result in amplification of the dynamic forces acting on the track. This amplification contributes to the degradation process of ballast and subgrade, ultimately resulting in the deterioration of vertical track geometry (settlement).To analyse and predict the accumulated settlement of the track in transition zones, a methodology using the iterative procedure is proposed. The methodology includes the finite element simulations of the vehicle-track and sleeper-ballast interaction during a train passing a transition zone; and iterative calculations of accumulated track settlement, based on an empirical model for ballast settlement.The simulations are performed using a 3-D dynamic finite element model (explicit integration) of a track transition zone, which accounts for the differential stiffness and the differential settlement of the track. Also, nonlinear contact elements between sleepers and ballast are used. As a result, the model can perform the detailed analysis of the stresses in ballast and accounts for the effects of vehicle dynamics. The model was validated against field measurements. The empirical settlement model describes the two-stage settlement of ballast and the nonlinear relationship between ballast stresses and permanent settlement.The proposed methodology is demonstrated by calculating the track settlement in the transition zone for 60,000 loading cycles (3.5 MGT). The dynamic responses such as ballast stresses are analysed to study the effect of the settlement. The parametric study of the iteration step used in the accumulated settlement procedure has been performed, based on which the optimal step is suggested.

PREDICTION OF BEHAVIOUR OF PRESTRESSED SUSPENSION BRIDGE WITH TIMBER DECK PANELS

Cable truss usage allows developing bridges with reduced requirements for girder stiffness, where overall bridge rigidity is ensured by prestressing of the stabilization cable. The advantages of prestressed suspension trusses to provide required stiffness without massive stiffness girders and the ability of cross-laminated timber to behave in both directions are combined in the analysed structure. Prestressed cable truss with coincident (unclear meaning, difficult to translate) in the centre point of the span main and stabilization cables and vertical suspenders only was considered as the main load carrying system in the considered structure of suspension bridge. Two numerical models evaluated influence of cross-laminated timber deck on the behaviour of prestressed cable truss. Two physical models of the structure with the span equal to 2 m were developed for verification of the numerical models. The first physical model was developed for the case, when panels of the deck are placed without clearances and behaving in the longitudinal direction in compression so as in the transversal direction in bending. The second physical model was developed for the case when panels of the deck are placed with clearances and are behaving in the transverse direction in bending only. The dependences of maximum vertical displacements and horizontal support reaction of the cable truss on the intensity of vertical load in cases of symmetric and unsymmetrical loading were obtained for both physical models. Possibility to decrease the cable truss materials consumption by 17% by taking into accountcombined work of prestressed cable trusses and cross-laminated timber panels was stated.

Floor Heave Mechanism of Gob-Side Entry Retaining with Fully-Mechanized Backfilling Mining

Serious floor heave in gob-side entry retaining (GER) with fully-mechanized gangue backfilling mining affects the transportation and ventilation safety of the mine. A theoretical mechanical model for the floor of gob-backfilled GER was established. The effects of the mechanical properties of floor strata, the granular compaction of backfilling area (BFA), the vertical support of roadside support body (RSB), and the stress concentration of the solid coal on the floor heave of the gob-backfilled GER were studied. The results show that the floor heave increases with the increase of the coal seam buried depth, and decreases with the increase of the floor rock elastic modulus. The development depth of the plastic zone decreases with the increase of the c and φ value of the floor rock, and increases with the increase of the stress concentration factor of the solid coal. The development depth of the plastic zone in the test mine reached 2.68 m. The field test and monitoring results indicate that the comprehensive control scheme of adjusting backfilling pressure, deep grouting reinforcement, shallow opening stress relief slots, and surface pouring can effectively control the floor heave. The roof-floor displacement is reduced by 73.8% compared to that with the original support scheme. The roadway section meets the design and application requirements when the deformation stabilizes, demonstrating the rationality of the mechanical model. The research results overcome the technical bottleneck of floor heave control of fully-mechanized backfilling GER, providing a reliable basis for the design of a floor heave control scheme.

Stauffer Cathedral: A Post-Modern Library

Completed in October 1994, the Joseph S. Stauffer Library is undoubtedly an audacious new addition to the landscape of Queen's University. Its innovative design, coupled with the library's emphasis on electronicbased learning, distinguishes the building as a product of the contemporary period. When examining the structure's aesthetic elements, however, its skeletal exterior frame, lofty interior spaces, and rising vertical supports recall the tenants of a much older tradition – those of Gothic architecture. This paper will examine the use of post-modern architectural theory by the library's architects and the homage paid to Gothic architectural traditions in order to place Stauffer Library in the long history of collegiate architecture.

Analysis of the Dynamic Wheel Loads in Railway Transition Zones Considering the Moisture Condition of the Ballast and Subballast

Transition zones in railway tracks are the locations with considerable changes in vertical support structures, e.g., near bridges. Due to possible water flow constrictions in transition zone structures, there is frequently an increased moisture level in the ballast/subballast layers, which is a potential source of track degradation. This paper presents results of the moisture condition measured in three transition zones using ground penetrating radar, where the ballast/subballast are analyzed. The relationship between the moisture condition and track degradation in the transition zones is studied by comparing it to the longitudinal track level that is measured by the track inspection coaches. A strong connection is found between the high moisture condition and track degradation in the transition zones. The dynamic behavior of the transition zones with high moisture condition is analyzed using the Finite Element method. Differential stiffness and settlement are taken into consideration in the transition zone model, which is also coupled with a vehicle. The ballast/subballast layers are modelled as solid elements. Increased moisture conditions are considered as a reduction of elastic modulus, according to laboratory findings. Results show that high moisture leads to an increase of dynamic wheel loads in the transition zone, which explains the connection and confirms that the high moisture condition is a source of transition zone problems.

Multi-spectral plasmon induced transparency based on three-dimensional metamaterials

We theoretically and numerically demonstrate multi-spectral plasmon induced transparency (PIT) in three-dimensional metamaterials comprising of parallel nanorods and a vertical nanorod. By moving the vertical middle nanorod to break the structural symmetry, the structure presents single-spectral or dual-spectral PIT windows, while it exhibits multi-spectral PIT windows at the laser wavelengths with He-Ne, ruby Cr3+ and Kr, via moving the bottom nanorod. The quasi-static interaction model reveals that the near-field coupling strength between nanorods increases with the movement of the nanorod. The coupling strength between nanorods is enhanced, which makes vertical middle nanorod support dipole and quadrupole modes and further results in multi-spectral PIT by bright-dark mode coupling. This work provides a way to obtain multi-spectral PIT in an easily fabricable nanostructure, and it may achieve potential applications in a variety of fields including filters, sensing, and some other nanoplasmonic functional devices.

Pool temperature stratification analysis in CIRCE-ICE facility with RELAP5-3D© model and comparison with experimental tests

In the frame of heavy liquid metal (HLM) technology development, CIRCE pool facility at ENEA/Brasimone Research Center was updated by installing ICE (Integral Circulation Experiments) test section which simulates the thermal behavior of a primary system in a HLM cooled pool reactor. The experimental campaign led to the characterization of mixed convection and thermal stratification in a HLM pool in safety relevant conditions and to the distribution of experimental data for the validation of CFD and system codes. For this purpose, several thermocouples were installed into the pool using 4 vertical supports in different circumferential position for a total of 119 thermocouples [1][2].The aim of this work is to investigate the capability of the system code RELAP5-3D© to simulate mixed convection and thermal stratification phenomena in a HLM pool in steady state conditions by comparing code results with experimental data. The pool has been simulated by a 3D component divided into 1728 volumes, 119 of which are centered in the exact position of the thermocouples. Three dimensional model of the pool is completed with a mono-dimensional nodalization of the primary main flow path. The results obtained by code simulations are compared with a steady state condition carried out in the experimental campaign. Results of axial, radial and azimuthal temperature profile into the pool are in agreement with the available experimental data Furthermore the code is able to well simulate operating conditions into the main flow path of the test section.

DETERMINATION AND RANGING OF ORGANIZATIONAL AND TECHNOLOGICAL FACTORS THAT DEFINE THE RATIONAL DECISIONS OF RE-BARS CONNECTION

Purpose. The paper proposes: 1) determination and formulation of factors that influence the choice of rational method for joining re-bars of vertical support members of reinforced concrete frame; 2) determination of factor parameters; 3) ranging of factors by the expert evaluation (Delphi) method. Methodology. In order to achieve research objectives, it is necessary to carry out analysis of existent rebar connection methods, determination of factors and parameter variation limits for each of the methods. Performing factor ranking by the expert evaluation method. Findings. The results of the questioning materials of 14 experts in the area of monolithic construction allowed setting the following: when choosing the rational re-bars connections, the most significant values are the factors that define the time parameters: possibility of carcassing, time of joining the re-bars, length of rebar cage, prior operation run time, operation time of main lifting equipment. Herewith the factors that define the rebar cage parameters have a direct relation to the work performance time, as they determine the amount of bar connections in the course of building erection over wide range. Economic factors – rebar connection cost and quality control cost – have the less value. It is obvious that in the conditions of considerable construction expenses it is advantageous for an investor to increase the rebar joining cost for the work growth rate. Structural and technological factors have the least value: origin of eccentric load transmission between re-bars, possibility of use of the thermally work-hardened re-bars of А500 and higher grades, work category for implementation of works, necessity to use the scaffold and appurtenances for re-enforcement of constructions. The reason is analogical: a contractor is ready to go to complication of technology with the purpose of reduction of the facility erection terms. As the calculated Pearson’s matching criterion χ2 = 47.24 is higher than the tabular one (22.36203), then the obtained concordance coefficient W=0.26 is not casual value, and that is why the obtained results make sense and can be used in further researches. Originality. The author obtained factors that influence the choice of the rational method for re-bars connection the most. Practical value. Ranging of factors will allow objective approaching to the problem of choice of re-bars connection method, optimizing the labour and material costs, and also reducing the construction time.

The befuddling nature of mouse lemur hands and feet at Bezà Mahafaly, SW Madagascar.

The reddish-gray mouse lemur (Microcebus griseorufus) possesses striking phenotypic and behavioral variation. This project investigates differences in autopod proportions in neighboring populations of M. griseorufus from the Special Reserve at Bezà Mahafaly in southwest Madagascar. One population resides in an environment generally preferred by M. griseorufus-a spiny forest with large-trunked trees, vertically-oriented supports, and more open ground, while the other resides in a gallery forest with abundant small, often horizontal peripheral branches in high canopy. We demonstrate significant interpopulation differences in autopod morphophology despite no evidence of divergence in mitochondrial cytochrome b. We test two hypotheses regarding ultimate causation. The first, based on the Fine Branch Arborealism Hypothesis (FBAH), holds that autopod differences are related to different locomotor practices in the two environments, and the second, based on the Narrow Niche Hypothesis (NNH), holds that the observed differences reflect a relaxation (from ancestral to descendant conditions) of selective pressure for terrestrial locomotion and/or use of large, vertical supports combined with positive selection for locomoting in peripheral branch settings. Our data conform well to FBAH expectations and show some support for the NNH. Individuals from the gallery forest possess disproportionally long posterior digits that facilitate locomotion on small, flexible canopy supports while individuals from the spiny forest possess shorter posterior digits and a longer pollex/hallux that increase functional grasping diameter for large vertical supports and facilitate efficient ground locomotion. Focal individual data confirm differences in how often individuals descend to the ground and use vertical supports. We further show that predispersal juveniles, like adults, possess autopod morphologies suited to their natal forest. We explore two proximate mechanisms that could generate these cheiridial differences. The first posits an in vivo plastic response to different locomotor behaviors, the second posits differences that manifest in early development.

Parsec-scale Obscuring Accretion Disk with Large-Scale Magnetic Field in AGNs

Abstract A magnetic field dragged from the galactic disk, along with inflowing gas, can provide vertical support to the geometrically and optically thick pc-scale torus in AGNs. Using the Soloviev solution initially developed for Tokamaks, we derive an analytical model for a rotating torus that is supported and confined by a magnetic field. We further perform three-dimensional magneto-hydrodynamic simulations of X-ray irradiated, pc-scale, magnetized tori. We follow the time evolution and compare models that adopt initial conditions derived from our analytic model with simulations in which the initial magnetic flux is entirely contained within the gas torus. Numerical simulations demonstrate that the initial conditions based on the analytic solution produce a longer-lived torus that produces obscuration that is generally consistent with observed constraints.